Monday, September 17, 2012

Dry spell continues.. only 2 mm of rain in Winnipeg since mid August

Rainfall over past 30 days across Prairies. Note large area with little or no rain from southern AB to southern MB

It's been an exceptionally dry 4 weeks over the Red River valley with very little in the way of storms systems affecting southern Manitoba, or much of the southern Prairies for that matter (see top image left). In Winnipeg, only 2 mm of rain has fallen since August 15th, with only 4 days of minimal precipitation in that time. (NOTE: Winnipeg airport has recorded some false precipitation readings since August 15th, resulting in slightly higher amounts than actually have fallen)

Normally we should see about 52 mm of rainfall in September, but we're far from that pace, and the prospects for significant rain in the next week or so are not promising. A system dropping from the Interlake may give us some rain overnight Tuesday into Wednesday morning, but at this point, amounts only look to be in the 2-5 mm range for Winnipeg, far from enough to ease soil moisture concerns. Other than that, things look persistently dry through the next week or so. Soil moisture levels are getting very low across the RRV, after a dry summer that saw only about half the normal rainfall. This will become more of a concern for farmers if adequate moisture is not received by winter freeze up.

35 comments:

So what’s the reasoning behind this dry spell this time? It would appear that all of western Canada has been under a big dry spell for the last month but more so southern Manitoba for the whole summer whereas areas farther west saw a lot more earlier in the summer. We've been on the northern periphery of the US drought has it been the same reason for the last month? Something I've noticed is lack of being on the eastern end of an upper trof is why its been so dry.

@anon.. I think it's just a continuation of the pattern we've seen over the past few months where systems have been bypassing us ( mainly to our north ) and we keep missing precip events. This is amplified in the late summer/fall when we lose the higher dewpoints that drive convection... which also partly explains the change to dryness out west. Plus, over the past month, we've seen a greater frequency of upper ridges over BC/AB which also tends to give a drier pattern over the Prairies.

Whatever the reason, the dryness is becoming quite evident here. Lawns are yellow and cracking, and water levels are low. It's getting tougher on the wildlife as well. The other day I drained my pool in the back, and soon there were dozens of birds flocking to the area where the water was collecting. Standing water is nowhere to be found. It's almost like it's forgotten how to rain around here..

Frost a pretty good bet over much of the RRV and SE MB tonight as skies clear and winds drop off. Winnipeg however may be spared from a more widespread freeze tonight, especially at the airport. We have a southerly flow developing overnight which will keep temps up a bit, including at the airport where a southerly flow is off the warmer city (as opposed to that unmoderated rural NW flow). We also have some high cloud upstream that should be spreading in overnight to also help insulate things. Highest frost risk in Winnipeg will be between midnight and 3 am as temps bottom out towards the freezing mark, with temps stabilizing or even rising overnight as the clouds move in and southerly flow picks up. Better chance for subfreezing temps over southern and eastern suburbs, and areas south and east of the city.

System over northern SK drops through the MB interlake overnight and into NW Ontario Wednesday with area of rain associated with it. Rain could be pushing into Winnipeg overnight into Wednesday morning, with a greater liklihood of precip to our north and east. NAM giving Winnipeg around 5 mm of rain beginning overnight and ending Wed am, while GEM only gives us about 1 mm (which is at odds with forecast for Winnipeg calling for "clearing" tonight) Greater amounts of 5-10 mm shown through Lake Winnipeg areas.

Behind this system we have a reinforcing shot of cool air, with lake effect rainshowers developing off Lake Winnipeg Wednesday into Thursday, affecting areas mainly east of Winnipeg.

Hey rob, sorry I haven't posted a comment in a while I'm just curious do you think we have a chance anytime soon for very weak thunderstorms, with the low pressure systems forecast to come through our area? We really didn't have a good season overall in Manitoba for even the smallest and dormant storms, as well our last Event occurred sometime in August I think and has been really quiet since. Any chance in the near future or will we have to wait for next spring for storms?

Mike.. I really don't expect anything more this season thunderstorm wise. It's possible we may see an isolated thunderstorm (non severe) into early October provided we get an energetic system with good dynamics.. but otherwise, the odds of thunderstorms this late in the season are growing pretty slim.

Models do show however some pretty good lake effect showers coming off Lake Winnipeg later tomorrow into Wednesday night with a good band setting up through the Bissett/Whiteshell areas. Some moderate rain possible in that band. Some pretty strong NW winds setting up over southern Lake Winnipeg as well Wednesday morning with gusts to 45 knots (70-80 km/h) possible.

Yes Rob. WeatherFarm is serving up CYWG weather, while WeatherBug has issues. They are both forecasting a low of 4C tonight which is rather chilly compared to everything else (they both also have yesterday's frost warning still showing). But then on WeatherFarm if you check the hourly forecast, it stays between 12-17 C all night, so their own forecasts aren't matching. Other products aren't working right either. Lots of bugs.

I have my station on the WeatherBug network here in Regina and I also see the same behavior with stations sometimes showing up and other times not. Also the data from another station being displayed or a different label on the data.

Seems that if a station is not reporting for a certain length of time the system extrapolates and substitutes a nearby source.

Still little or no rain here in Winnipeg. Area of rain just to our north and east moving to the southeast. We may get clipped with some rain as area slips by, but overall, not much to help us with our moisture deficit.

Strong NW winds over southern MB this morning behind system moving into NW Ontario with gusts of 70-80 km/h. Gale warnings out on the lakes with winds gusting to 43 kts (80 km/h) in Victoria Beach right now. Waves of 1.5m being reported from the south basin buoy and rising.

More than one source has indicated that the Arctic Ice melt has (and is) effecting our weather specifically by altering the "jet stream" and delaying the speed of changes in the weather in weather patterns. ( cold dry becomes much colder much dryer for longer)How are the models and forecasters incorporating this change in their forecasts?

Anonymous.. I'll post some comments from Wunderground's informative link on Arctic sea loss, which addresses your question. (click on my name for link to complete article..)

"Continued loss of Arctic sea ice may dramatically alter global weather and precipitation patterns in the decades to come. The jet stream will probably move further north in response to warmer temperatures over the pole, which will bring more precipitation to the Arctic. More frequent and intense droughts over the U.S. and other regions of the mid-latitudes may result from this shift in the jet stream. Changes to the course of the jet stream affect weather patterns for the entire planet, and we can expect impacts on the strength of the monsoons and recurvature likelihood of hurricanes. During 1979 to 2006, years that had unusually low summertime Arctic sea ice also had a 10-20% reduction in the temperature difference between the Equator and the North Pole. This resulted in reduced winter precipitation over all of the U.S., Alaska, and Northern Europe. In contrast, increased precipitation fell over Spain, Italy, and Japan during these winters. Although intense La Niña or El Niño events can have a much stronger influence on wintertime weather patterns, reduced summertime Arctic sea ice should give most of the Northern Hemisphere a delayed start to winter during most years for the foreseeable future."

Note that NOAA announced today that Arctic sea ice has reached a record low minimum this year.

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